33/11 KV Sub Station
33/11 KV Sub Station
3311 KV Sub Station.ppt (Size: 2.58 MB / Downloads: 1329)
Main Equipments in 33 KV Sub-Station
1) Power transformer
2) Circuit breaker
4) Earthing switch
5) lightning arrestor
7) Current transformer
8) Potential transformer
9) Protective relay
10) DC battery set
12)Fire fighting system
Transformer is used to step down the voltage from 33 kv voltage to 11kv voltage .
Generally 3.15 MVA, 5 MVA, 10 MVA 33/11kv, Δ / Y transformer are used in 33/11kv s/s.
Maintenance of Transformers
Check Oil level in main tank & OLTC tank.
Check the color of silica gel in breather ;it must be blue in color .if it is turned pink then recondition it or replace it.
Check On load Tap Changer Lower/Raise trail by Local & Remote.
Trip trail by draining oil in Buchholz relay
Check Earth resistance ,provide watering arrangement for earthling pits.
Tight all connections.
Check breakdown voltage of oil.
Clean the bushings.
Attend the oil leakages
Note Temperature of Oil & leakage.
It’s mineral oil obtained by refine crude petroleum. It serves the following purpose.
Provide additional insulation.
Carries away the heat generated in the core & coils.
Protects the paper from dirt & moisture.
Current T/F is used for protection and metering purposes.
It steps down the current level of the line for following purposes.
1) Measurement : ammeter , kw meter , kwh meter , power factor meter
2) control and protection : current when exceeds the set value operates the relay which senses the faulty condition .
Potential Transformer (P.T)
It steps down the voltage level of line for -
1) Measurement : voltmeter, frequency meter ,kw meter, kwh meter ,power factor meter
2) Control & protection : used in directional over current protection and under frequency relay operation (48.8 Hz , df/dt relay)
Circuit Breaker can switch automatically during normal and abnormal conditions . during faulty condition the fault is sensed by the relay and operates the circuit breaker to isolate the fault.
In 33kv substation generally vacuum circuit breaker are used where are quenching medium is vacuum
Advantage of Vacuum Circuit Breaker
1) no oil is required for are quenching
2) least maintenance
3) compact size
4) light in weight
Maintenance of circuit breaker
1) close/trip through local/remote control
2) trip trial through auto closer relay
4) oiling & greasing of moving parts
5) vermin proofing
6) heater healthy